The present invention relates to a decorative relief finish process. More particularly, it relates to a method of uniformly flattening or press-leveling excessive projections on the irregularly or unevenly roughened surface of an undercoat to a desired thickness to form a relief finish surface of desired decorative appearance.
Hitherto, decorative relief coatings having an irregularly or unevenly roughened surface have been formed by applying to a substrate such as a wall, for example, a spraying material or a coating material consisting mainly of coating composition, cement or plaster with a spray gun or a coating roller. These materials are used for undercoats as either primers of intermediate coating materials or as surfacers. The coated surface is ordinarily covered with a finishing topcoat. However, since these undercoats have irregular or uneven surfaces, it is customary to sand or polish or press excessive projections on the surface to level the thickness of the projections, thereby providing a more decorative topcoating or improving other functions of the uneven pattern, for example, to reduce the ability of the surface to be soiled.
There are largely two types of conventional methods of leveling excessive or unnecessary projections on an irregularly roughened topcoat surface. The first type is a method which involves sanding excessive projections with a sanding device after the coating is fully dried. The second type is a method involving rolling a roll made of rubber, Teflon, aluminum or stainless steel and having a smooth surface on the coated surface which is partially hardened by being left to stand for a few hours, the roll being wetted with a liquid which has an affinity with the spraying material or the coating material, i.e. the materil is soluble in the liquid. Although the former method can provide a favorable finish when the coarseness of the sanding device is carefully chosen, this method has the disadvantages that it will usually take at least half a day, or during cold weather several days, for the coatings to become hardened sufficiently for sanding, and that dust is produced during sanding so that this method is undesirable from the sanitary point of view. This method requires fairly large amounts of manual work, and skilled laborers, and frequent changing of the sanding device due to clogging of the sanding device. The latter method, on the other hand, has the advantage that handling is simple, since it involves merely rolling a roller on the coated surface, without the formation of dust. However, this method also has disadvantages, in that the time required for rolling will be dependent upon the wetting condition of the roller since the roller tends to stick or adhere to the surface, and that a large amount of the surface material may become detached from the coated mass on the surface by adhering to the roller and then be transferred to another place, thereby causing fluff projections which impair the appearance of the decorative relief finished surface. This may also lead to a decrease in workability. Particularly, this conventional method has the disadvantage that when a wide area of the wall surface is treated, the roller has to be wetted a plurality of times during the treating operation. In another case, too, in which a two-pack hardenable epoxy resinous coating material is employed, the application of this method is inappropriate because the coating composition will rapidly become completely hardened before it is possible to complete the treatment of the entire wide area of the uneven surface.